How is the ride when charged up? Since you drop so fast I worry that your reservoirs of pressure are dead. Without a reservoir of pressure any leak immediately takes the car down.

Try putting the lever to the lock position and see how fast it goes down. Without external leaks you have two possibilities. The first is the height valves. Putting the system in the lock position will prevent leaking level valves from leaking the system down. The second mechanism is leaks past the shock piston. This leak is captured and there is a spec for the acceptable volume, but it is real hard to test. This manner of leak is not stopped by the lock position.

I would check this first but the results are not exact as the mastervalve itself can leak internally back to the reservoir.

All of these leaks are internal and will not lose fluid. Unless your accumulators (pressure reservoirs) are new they need replacing. If there are leaks they are undoubtably due to running on dead accumulators. Running on dead accumulators feels like riding a buckboard; harsh, bouncy. Try bouncing each corner.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician